Please, stop using words without understanding what they mean. "Casual" play has nothing to do with skill, it has to do with how often a person plays and how seriously he/she takes gaming. Casual player might be one of the best players in the world who recently, say, won a championship and retired, but still plays from time to time - for example, Sean Plott is a casual Starcraft 2 player, even if he has won a Starcraft 1 USA championship at some point of his life and is VERY good at Starcraft 2 (he claims to have 3 separate accounts for each race, each having a Grandmaster status - looking at his macro skills in his Monobattles dailies, I'm inclined to believe him). Or someone might just be very talented at a game but not interested in playing it seriously, he just logs in once a month and destroys everyone - pretty much like Paul Morphy in Chess who had played for years very casually, not caring about studying theory or anything like that, and yet he was definitely the best player in the world.
There are no "casual games". There are casual gamers, and they might be both very bad and very good in terms of skill.
Both LoL and HotS are very friendly towards casual players. A person can open the game the first time in his life and get into action right away. Compare it to, say, Europa Universalis where, if you don't know how to play, you just won't be able to do anything meaningful, only some random actions without understanding what's going on in the game - now that game, indeed, requires some dedication to start really enjoying it. But LoL - no, you can enjoy it since the first second in game.